The present invention pertains to an apparatus for releasably coupling two movable bodies, and, more particularly, to an articulated ship employing a coupling arrangement permitting both rigid and flexible interconnection.
The use of tug-barge combinations for transporting cargoes by water offers many advantages over the use of self-propelled vessels such as tankers and the like. While the tug-barge combination can be used quite successfully in calm or sheltered water, the push-towing technique is generally unsuitable for open water travel because of the severity of conditions frequently encountered. In an attempt to reap the economic advantages afforded by tug-barge arrangement and yet overcome the adverse conditions encountered in open water travel, numerous articulated ships have been proposed. These articulated ships have taken numerous forms including both rigidly coupled systems and systems employing flexible coupling, i.e. systems allowing certain substantial relative movements of the coupled vessels. Examples of rigidly coupled vessels are disclosed in such patents as U.S. Pat. Nos. 3,610,196 to Lowry, 3,735,722 to Hooper et al and 3,486,476 to Breit, Jr. U.S. Pat. Nos. 3,756,183 and 3,605,675 to Clemence, Jr., and 3,568,621 to Kawasaki all disclose systems in which the articulated ship is flexibly coupled.
It is apparent from the prior art, as exemplified above, that both rigidly coupled and flexibly coupled systems have advantages. In terms of acting as a unitary ship, the rigidly coupled system far surpasses that of the flexibly coupled system. On the other hand, in terms of maneuverability in heavy seas, it may be desirable that certain relative motions of the two vessels be allowed while others be prevented as much as possible. In such cases, the flexibly coupled system may be preferred. As noted above, while both types of systems are disclosed in the prior art, there are no known practical systems by which both types of coupling can be accomplished with the same apparatus. It should also be pointed out that in rigidly coupled systems heretofore disclosed, relative draft engagement of the coupled vessels has been limited to a plurality of discrete draft engagements rather than continuous relative draft engagement within the draft limits of the vessels.